Your old television set has a confession to make: it’s toxic, with several pounds of lead in its picture tube. Unless you’ve already upgraded to a flat panel or liquid crystal display (LCD) model, you’ve got an environmental hazard on your hands.

Americans dumped an estimated 20.6 million older TVs into landfills in 2005, according to the Environmental Protection Agency (EPA). That’s 639,500 tons of metal, glass and plastic—equal to the weight of nearly 320,000 cars. It also means 59 million pounds of lead, which could potentially leach into streams and drinking water if not properly managed, says Jon Myers, director of public affairs for the California Integrated Waste Management Board.

Even if you’re still holding on to it, your old TV’s days may be numbered. Next year, the country’s broadcasting systems will complete the digital transition. For more than 50 years, your local TV station has beamed its analog broadcast signal free to your living room. No more, says the Federal Communications Commission (FCC). Beginning on February 17, 2009, all signals will be sent digitally—and older analog TVs connected to outdoor antennas or indoor “rabbit ears’ will go dark.

Luckily, there are options. You’re fine if your older TV is connected to cable, satellite or another pay TV service. And if you’re not connected, you still have until March 31 next year to apply online or by mail for a free government-approved $40-value coupon to buy a converter box that will keep the old sets working.

Even with these options, old TVs are becoming obsolete. Packrats will stow their old sets in the attic, gamers will use them as an extra screen and philanthropists will donate them to charity. But ask the EPA or the FCC or the eight states with TV recycling laws, and they’ll tell you this: They’re worried about people throwing them away.

How many? No one knows for sure. Expectations are in the tens of millions, perhaps as many as 80 million, says John Shegerian, co-founder and CEO of Fresno, Calif.-based Electronics Recyclers International. “It’s late, and most states have done nothing to prepare,” he says.

Parker Brugge, senior director and environmental counsel for the Consumer Electronics Association, says it’s not likely all of those TVs will end up in the garbage. “We’re trying to make that number as small as possible.” The problem is, relatively few consumers know about the greener alternatives for their toxic tubes. Myers says ignorance may fuel illegal dumping—when people toss their TVs into backyards or on the side of the road. “[That’s when] toxins almost certainly get into local waterways, and that concerns us most,” he says. “We’re getting better, we’re reducing it, but nationally it’s still a big problem.”